Snap-fit connection

ABSTRACT

Snap-fit connection for piece parts of hard material. Shoulders of opposite bevel that border an annular ring portion of one of the parts engage in wedgelike fashion shoulders of opposite bevel that border an annular recess portion of the other part.

United States Pareni i 1 e an Inventors Laurence G. 110mm 226 Fountain81., New Haven, Conn. 06515;

Donald .1. Mattis, 15 Douglas Drive, Norwalk, Conn. 06850 Mar. 9, 1970Continuation-impart of Ser. No. 1177, filed Jan. 7, 1970 Patented Aug.3, 1971 Appl. No. Filed SNAP-FIT CONNECTION 11 Claims, 7 Drawing Figs.

U.S. Cl 287/20 111, 24/2 1 7 Int. Cl Fllfib 9/00 Field of Search 24/208R,

208 A, 216, 217,108;287/20, 23;85/D1G. 2

[56] References Cited UNITED STATES PATENTS 2,912,712 11/1959 Shamban eta1. 85/D1G. 2 3243,858 4/1966 Melanson 24/208 A FOREIGN PATENTS 13,3651910 Great Britain..... .1 24/216 600,997 8/1934 Germany 24/208 APrimary E.ruminer David J. Williamowsky Assistant Examiner-Andrew V.Kundrat Attorneys-E. Manning Giles and J. Patrick Cagney ABSTRACT:Snap-fit connection for piece parts of hard material. Shoulders ofopposite bevel that border an annular ring portion of one of the partsengage in Wedgelike fashion shoulders of opposite bevel that border anannular recess portion ofthe other part.

PATENTEU Am; 319?! SNAP-FIT CGNNECTI'UN The present application is acontinuation-in-part of pending application entitled, Mechanical RemoteControl Apparatus, a plication Ser. No. 1,177 filed Jan. 7, 1970, andassigned to assignee of the present invention.

BACKGROUND OF THE INVENTION The present invention generally relates tomechanical connections and, more specifically, relates to snap-fitconnections for hard materials.

It is often desirable in the assembly of various products to be able tosnap-fit piece parts together instead of using a threaded connection.One drawback to snapfit connections which has reduced the incidence ofits use in product manufacture is the tendency of the connection to loseits strength with use thereby allowing the connected parts to wobble orbecome easily separated.

In the case of hard molded parts, considerations of mold design and easeof removal of a part from the mold add to the difficulties of adaptingsuch molded parts for snap-fit interconnection.

SUMMARY OF THE INVENTION Accordingly, it is a primary object of thepresent invention to provide a firm, high-strength, snap-fit connectionfor members of hard material that will retain its strength during usage.

A more specific object of the invention is to provide such a snap-fitconnection that is suitable for hard molded members withoutnecessitating complex mold design or problems of removal ofa part fromthe mold.

Briefly, the snap-fit connection of the present invention achieves theseobjectives as a consequence of unique wedgelike engagement betweenshoulders of opposite bevel that border an annular ring portion of oneof the connected members with shoulders of opposite bevel that border anannular complementarily shaped recess portion of the other member.

A more complete understanding of the invention, its objects, andadvantages will be had after reference to the detailed discussion tofollow and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings forming apart of the specification and in which like numerals are employed todesignate like parts throughout the same:

FIG. l is an elevational view, partly in section, showing a portion ofthe control unit ofan outside rearview mirror which incorporates thesnap-fit connection of the present invention;

FIG. 2 is a section taken as indicated at 2-2 ofFlG. ll;

FIG. 3 is an enlarged fragmentary detail view of snap-fit connectionstructure in accordance with the present inven tion;

FIG. t is a fragmentary detail view illustrating the snap-fit connectionin an end closure or cap arrangement;

FIG. 5 is a section view taken as indicated at 5-5 of FIG. 4i;

FIG. 6 is a fragmentary detail view of the knob portion of the ignitingunit of an electric cigar lighter and illustrating the snap-fitconnection in a snapring arrangement; and

FIG. 7 is a section taken as indicated at 7-7 of FIG. s.

DETAILED DESCRIPTION FIGS. 1-3 illustrate a portion of the control unitof a remote control rearview mirror which is the subject of the abovenoted copending application.

As more fully described therein, the control unit 20 is mounted uponinterior automobile door panel P and is shown to include a cable guidebracket 22 disposed within the door space, a support seat 23 having asocket portion 24 for snap-fit connection to a plug portion 25 of theguide bracket, and a bezel 27 mounted on the exposed face ofthe doorpanel P and having a circular wall 27W projecting into screw-threadedengagement with the threaded outer periphery 235T of the actuator seat23. These parts are clamped to the door panel by turning the bezel 27onto the actuator seat 23 to draw the actuator seat forwardly until theguide bracket 22 clamps against the panel I.

The connection between the bracket plug 25 and the socket portion 24 ofthe actuator must be of high strength to enable a firm clamping actionto be maintained between the bezel 2d, the guide bracket 22 and thevehicle door panel P.

To provide such high strength connection and in accordance with thepresent invention, the bracket plug portion 25 is shown to have alengthwise or axial tapering cylindrical sidewall portion 25W providedwith a radially outwardly extending annular ring portion 25R oftrapezoidal profile (See FIG. 3 presenting a lengthwise or axiallytapered cylindrical surface 25C bordered at opposite ends by obliqueannular shoulders 2553, 2ST of opposite bevel. The socket portion 24 forreceiving the plug has an annular wall 2AA (FIG. 3) defining a centralsocket 5 having a cylindrical sidewall portion MW (FIG. 3) ofcorresponding lengthwise taper. The annular wall IBM. terminates in acircular array of three symmetrically spaced cantilever leg portions 24Lthat are of complementary arcuate shape (See FIG. 2). The annular wall249A has a radially inwardly projecting internal annular recess 2 3R oftrapezoidal profile presenting a lengthwise tapered cylindrical surfaceMC bordered at opposite extremities by oblique shoulder surfaces 1M5, MTof opposite bevel.

To define the cantilever legs ML, the annular wall 24A is provided witha circular groove 240 and a set of three radial notches MN. The circulargroove MG opens endwise toward the plug 25 and encircles the centralsocket S to a depth beyond the adjacent shoulder surfaces 245 and theradial notches MN open endwise toward the plug 25 and lead from thecentral socket S to the circular groove 246. The groove and notchconfiguration enables the degree of leg flexing necessary to accommodateforce-fit insertion of the plug 25 into the central socket to effectseating of the annular ring 25R within the annular recess 24R in arelationship wherein the beveled shoulders MS and 25S engage inwedgelike fashion the beveled shoulders MT and 25T. The tapered plug andsocket structure provides automatic leadin and cooperates with thebeveled shoulders in achieving high strength against pullout. Thesnap-fit parts are otherwise free of axial engagement so that theseshoulders transmit the axial loads between the parts. This relationshipachieves an unusually high strength connection which resists pulloutunder all normal conditions. The strength of the joint against pulloutalso tends to increase with use.

In the embodiment illustrated in FIGS. ll--3 herein the snap-fit partsshown can be molded of stiff materials such as acetals as marketed underthe trademarks Delrin Celcon. The snap-fit arrangement facilitatesmolding and removal from the mold and, as will be more fully explainedhereinafter with reference to the embodiment of FIGS. 6 and 7, enablescomplex part configurations and surface treatments to be applied to theindividual parts prior to final assembly. A unitary structure withsurface coatings and other features could not be so provided in manyinstances. In the illustrated embodiment typical dimensions for apreferred snap-fit connection are:

a taper of 8 for the plug 25, the surface 25C, the central socket S andthe surface 24C; the beveled shoulders 248, MT, and 25S, 2ST are at 45to the center axis; the radial offset of each of the cylindricalsurfaces 24C, 25C

is about 0.010 inches; the diameter of the plug 25 is 0.431 inches atthe root of the beveled shoulder 25T; the diameter of the central socketS is 0.44l inches at the root of the beveled shoulder MT; the beveledshoulders MS and 255 are approximately 0.050 and 0.l 10 inchesrespectively, from the end of the socket and the groove 240 is 0.078inches deep, 0.03l inches wide and has a mean diameter of0.55l inches;and

the legs 24L have an inside diameter of 0.465 inches.

FIGS. 4 and 5 illustratethe snap-fit connection assembly as adapted foruse as an end closure or cap fitting. In this embodiment the one part isshown as a cup-shaped end closure or cap 125 fitted upon the second partwhich is shown as the end portion of a hollow cylindrically shaped tube124. It will be noted that this embodiment differs from that of FIGS.l-3 in that the inserted part 124 is provided with the annular recessedportion and the cap 125 is provided with the annular ring portion. Asshown in FIG. 5, the annular wall 124A of the tube 124 has a set ofthree radial notches 124N (only one shown), defining the arcuatecantilever legs 124L, opening endwise toward the cap 125 and leadingfrom the interior of the tube 124 to the sidewall 125R of the cap 125.It will further be noted that in the instant embodiment, a circulargroove is not required to define the cantilever legs 124L because thethickness of the annular wall 124A permits sufficient flexing. In allother respects, the description of the embodiment of FIGS. 1-3 apply sothat such need not be repeated.

FIGS. 6 and 7 depict the snap-fit connection assembly as incorporated ina handling knob assembly 200 of the igniting unit of a cigar lighterwherein one piece part is shown to com prise a knob shank 225 andanother to comprise a snapring 224 fitted about the shank.

As is well known to those skilled in the particular art, it is desirablethat the handling knob be assembled from individual parts rather than beof unitary construction as such facilitates flexibility and ease ofornamentation thereof. Thus, for example, in the specific arrangementshown herein, the knob cap 220 and snap ring 224 are of Black-Absplastic material while the shank 225 comprises Kralastic MP-2603finished with chrome plate.

Difficulties have been encountered when assembling the handling knobsfrom individual parts arising from the problem of providing a strongconnection between the parts while at the same time minimizing costs byutilizing molded plastic parts. The snap-fit connection assembly of theresent invention provides a ready solution to such difficulties.

What has been said in reference to FIGS. 1-3 above is applicable to theembodiment of FIGS. 6 and 7 and need not be repeated. Suffice it to saythat the snap ring 224 is provided with a circular groove (owing to thethickness of the sidewall portion 224R) opening endwise from the shank225 and with a set of three radial notches 224N (only one shown),defining the arcuate cantilever legs 224L, opening endwise toward thetop of the shank 225 and leading from the circular notch 2246 to thesidewall of the shank.

In each of the specific embodiments disclosed herein, both of theinterconnected parts have been described as being of a hard moldedplastic material. However, it will be appreciated that they need not beplastic and can be of other hard materi' als, such as brass.

Thus, while preferred constructional features of the invention areembodied in the structure illustrated herein, it is to be understoodthat changes and variations may be made by those skilled in the artwithout departing from the spirit and scope of the appended claims.

The embodiments of the invention in which We claim an exclusiveprivilege or property are defined as follows:

1. In a pair of snap-fit interconnected members having correspondinglyaxially tapering first and second generally cylin- 'drical sidewallportions in concentric overlapping relation,

Said first sidewall portion having an annular ring portion projectingtherefrom presenting a correspondingly axially tapered cylindricalsurface bordered at its opposite axial extremities by oblique shouldersurfaces of opposite bevel, said second sidewall portion having anannular recess therein accommodating said ring portion and presenting acorrespondingly axially tapered cylindrical surface bordered at itsopposite axial extremities by oblique shoulder surfaces of oppositebevel for wedgelike engagement with the shoulder surfaces of said firstsidewall portion, one of said sidewall portions terminates in a circulararray of spaced cantilever leg portions,

said leg portions having base regions located adjacent one of saidshoulder surfaces of the last-named sidewall portion.

2. In a pair of snap-fit interconnected members in accordance with claim1 wherein each of said sidewall portions are axially tapered atapproximately 8.

3. In a pair of snap-fit interconnected members in accordance with claim1 wherein each of said oblique shoulder surfaces are axially beveled atapproximately 45.

4. In a pair of snap-fit interconnected members in accordance with claim2 wherein each of said oblique shoulder surfaces are axially beveled atapproximately 45, said annular ring portion and said annular recessportion each being offset from the corresponding sidewall portion about0.010 inches.

5. In a pair of snap-fit interconnected members in accordance with claim1, said cantilever leg portions being of complementary arcuate shape intransverse section.

6. In a pair of snap-fit interconnected members in accordance with claim5 wherein each of said oblique shoulder surfaces are axially beveled atapproximately 45, each of said sidewall portions are axially tapered atapproximately 8, and said annular ring portion and said annular recessportion each being offset from its corresponding sidewall portion about0.0l0 inches.

7. In a snap-fit mechanical connection of first and second members, thefirst of said members having an axially tapering cylindrical sidewallportion, the other of said members having an axially taperingcylindrical sidewall portion terminating in a circular array ofsymmetrically spaced cantilever leg portions of complimentary arcuateshape in transverse section, each of said sidewall portions having aradially offset annular wall portion presenting a correspondinglyaxially tapered cylindrical surface bordered at its opposite axialextremities by oblique shoulder surfaces of opposite bevel, the offsetannular wall portion of one of said sidewall portions extendingoutwardly therefrom, the offset annular wall portion of the other ofsaid sidewall portions extending radially inwardly therefrom, the offsetannular wall portion of the sidewall portion of the second of saidbodies being located so that a portion of its axial extent interceptsthe base regions of said leg portions.

8. In a snap-fit mechanical connection as defined in claim 7, whereineach of said sidewall portions are axially tapered at approximately 8",each of said oblique shoulder surfaces being axially beveled atapproximately 45.

9. In a snap-fit mechanical connection as defined in claim 8, whereineach said offset annular wall portion is offset on the order of about0.0 l 0 inches.

10. A snap-fit mechanical connection assembly comprising, incombination, a pluglike member of hard molded plastic having alengthwise tapering insert body provided with a radially outwardlyprojecting annular ring portion presenting a correspondingly lengthwisetapered cylindrical surface bordered at opposite lengthwise extremitiesby oblique shoulder surfaces of opposite bevel, and a socket member ofhard molded plastic having an annular wall terminating in a circulararray of symmetrically spaced cantilever leg portions of complementaryarcuate shape in transverse section to border and define a centralsocket region opening endwise towards the plug member and ofcorresponding lengthwise taper, said annular wall having a radiallyoutwardly projecting annular recess in open communication with thesocket to present a correspondingly lengthwise tapered cylindricalsurface bordered at opposite lengthwise extremities by oblique shouldersurfaces of. opposite bevel, said recess being located so that a portionof its lengthwise extent intercepts the base regions of said legportions.

1!. A snap-fit mechanical connection assembly comprising, incombination, a plug member of hard molded plastic having a lengthwisetapering insert body provided with a radially outwardly projectingannular ring portion presenting a correspondingly lengthwise taperingcylindrical surface bordered at opposite ends by oblique shoulders ofopposite bevel, and a socket member of hard molded plastic having acentral socket of corresponding lengthwise taper, said socket memberhaving radial notches opening endwise toward the plug member and leadingfrom the socket to the groove at peripherally spaced locations about thesocket to provide a set of three leg portions for outward flexing toenable lengthwise insertion of the plug body into socket untilmechanical interlock of said ring portion in said recess is established.

1. In a pair of snap-fit interconnected members having correspondinglyaxially tapering first and second generally cylindrical sidewallportions in concentric overlapping relation, said first sidewall portionhaving an annular ring portion projecting therefrom presenting acorrespondingly axially tapered cylindrical surface bordered at itsopposite axial extremities by oblique shoulder surfaces of oppositebevel, said second sidewall portion having an annular recess thereinaccommodating said ring portion and presenting a correspondingly axiallytapered cylindrical surface bordered at its opposite axial extremitiesby oblique shoulder surfaces of opposite bevel for wedgelike engagementwith the shoulder surfaces of said first sidewall portion, one of saidsidewall portions terminates in a circular array of spaced cantileverleg portions, said leg portions having base regions located adjacent oneof said shoulder surfaces of the last-named sidewall portion.
 2. In apair of snap-fit interconnected members in accordance with claim 1wherein each of said sidewall portions are axially tapered atapproximately 8* .
 3. In a pair of snap-fit interconnected members inaccordance with claim 1 wherein each of said oblique shoulder surfacesare axially beveled at approximately 45* .
 4. In a pair of snap-fitinterconnected members in accordance with claim 2 wherein each of saidoblique shoulder surfaces are axially beveled at approximately 45* ,said annular ring portion and said annular recess portion each beingoffset from the corresponding sidewall portion about 0.010 inches.
 5. Ina pair of snap-fit interconnected members in accordance with claim 1,said cantilever leg portions being of complementary arcuate shape intransverse section.
 6. In a pair of snap-fit interconnected members inaccordance with claim 5 wherein each of said oblique shoulder surfacesare axially beveled at approximately 45* , each of said sidewallportions are axially tapered at approximately 8* , and said annular ringportion and said annular recess portion each being offset from itscorresponding sidewall portion about 0.010 inches.
 7. In a snap-fitmechanical connection of first and second members, the first of saidmembers having an axially tapering cylindrical sidewall portion, theother of said members having an axially tapering cylindrical sidewallportion terminating in a circular array of symmetrically spacedcantilever leg portions of complimentary arcuate shape in transversesection, each of said sidewall portions having a radially offset annularwall portion presenting a correspondingly axially tapered cylindricalsurface bordered at its opposite axial extremities by oblique shouldersurfaces of opposite bevel, the offset annular wall portion of one ofsaid sidewall portions extending outwardly therefrom, the offset annularwall portion of the other of said sidewall portions extending radiallyinwardly therefrom, the offset annular wall portion of the sidewallportion of the second of said bodies being located so that a portion ofits axial extent intercepts the base regions of said leg portions.
 8. Ina snap-fit mechanical connection as defined in claim 7, wherein each ofsaid sidewall portions are axially tapered at approximately 8* , each ofsaid oblique shoulder surfaces being axially beveled at approximately45* .
 9. In a snap-fit mechanical connection as defined in claim 8,wherein each said offset annular wall portion is offset on the order ofabout 0.010 inches.
 10. A snap-fit mechanical connection assemblycomprising, in combination, a pluglike member of hard molded plastichaving a lengthwise tapering insert body provided with a radiallyoutwardly projecting annular ring portion presenting a correspondinglylengthwise tapered cylindRical surface bordered at opposite lengthwiseextremities by oblique shoulder surfaces of opposite bevel, and a socketmember of hard molded plastic having an annular wall terminating in acircular array of symmetrically spaced cantilever leg portions ofcomplementary arcuate shape in transverse section to border and define acentral socket region opening endwise towards the plug member and ofcorresponding lengthwise taper, said annular wall having a radiallyoutwardly projecting annular recess in open communication with thesocket to present a correspondingly lengthwise tapered cylindricalsurface bordered at opposite lengthwise extremities by oblique shouldersurfaces of opposite bevel, said recess being located so that a portionof its lengthwise extent intercepts the base regions of said legportions.
 11. A snap-fit mechanical connection assembly comprising, incombination, a plug member of hard molded plastic having a lengthwisetapering insert body provided with a radially outwardly projectingannular ring portion presenting a correspondingly lengthwise taperingcylindrical surface bordered at opposite ends by oblique shoulders ofopposite bevel, and a socket member of hard molded plastic having acentral socket of corresponding lengthwise taper, said socket memberhaving a radially outwardly projecting annular recess in opencommunication with the socket to present a correspondingly lengthwisetapered cylindrical surface bordered at opposite ends by obliqueshoulders of opposite bevel, said socket member having a circular grooveopening endwise towards the plug member and encircling the socket to adepth beyond the adjacent bevel surface thereof, said socket memberhaving radial notches opening endwise toward the plug member and leadingfrom the socket to the groove at peripherally spaced locations about thesocket to provide a set of three leg portions for outward flexing toenable lengthwise insertion of the plug body into socket untilmechanical interlock of said ring portion in said recess is established.